The present invention relates generally to the field of digital communications, such as the communication of television, multimedia, and/or interactive entertainment and information signals. In particular, the present invention provides methods and apparatus for creating a Program Association Table (PAT) for a multiplexed data stream that is to be reduced to carry fewer services for, e.g., cable-side transmission via a cable television plant. More particularly, the present invention provides methods and apparatus for creating a PAT that represents a desired combination of multiplexed data stream subgroups contained within an incoming high data rate data stream, such as a high data rate Quadrature Phase Shift Keying (QPSK) modulated multiplexed data stream, when the incoming multiplexed data stream is to be reduced.
When processing high data rate satellite data feeds, it is often necessary to reduce the multiplexed data streams, e.g., for a cable-side multiplex. When reducing a high data rate data stream, some services (such as certain cable television channel services) are dropped. Only a subset of the services in the incoming high data rate data stream may appear in the reduced cable-side output data stream. Therefore, the original PAT of the incoming high data rate data stream may no longer be valid for the reduced multiplex.
It would be advantageous to provide methods and apparatus which allow a cable or satellite television headend decoder/transcoder to create and output a PAT which correctly corresponds to the services in the reduced data stream. It would be further advantageous to provide a high data rate data stream which comprises a predefined set of data stream subgroups, each of the subgroups containing a one or more services. It would be even further advantageous to provide predefined combinations of the data stream subgroups, each of which predefined combination produces a data stream with a desired reduced data rate. It would be still further advantageous to provide hidden PATs which correspond to each predefined combination of data stream subgroups, and to select a PAT corresponding to the desired subgroup combination for output with the desired subgroup combination as the reduced cable-side data stream.
The methods and apparatus of the present invention provide the aforesaid and other advantages.